<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button>按钮1</button><button>按钮2</button><button>按钮3</button><button>按钮4</button><button>按钮5</button>
    <script>
        var buttons = document.querySelectorAll('button');
        for (var i = 0; i < buttons.length; i++) {
            buttons[i].onmouseover = function() {
                for (var i = 0; i < buttons.length; i++) {
                    buttons[i].style.backgroundColor = '';

                }
                this.style.backgroundColor = 'pink';
            }
            buttons[i].onmouseout = function() {
                for (var i = 0; i < buttons.length; i++) {
                    buttons[i].style.backgroundColor = '';
                }
            }
        }
    </script>
</body>

</html>